A common method for forming cylindrical products from fibrous material, such as pipe insulation, is to helically wind rectangular strips of fibrous material on a mandrel, and place the mandrel within a mold where the material is heated and compressed to cure the binder on the fibers, thereby forming a cylindrical insulation product. A variation of this method is a batch process in which the fibrous material is clamped between two mold halves and then heated and compressed. Helical winding and batch processes are slow and require large amounts of capital and labor. Another process for producing cylindrical insulation products is a continuous molding process in which a strip of fibrous material is folded to a cylindrical shape and fed through a cylindrical mold which compresses and/or heats the material to cure it, thereby continuously producing a substantially rigid insulation product. A guide shoe is ordinarily used to continuously fold the flat strip of insulation material so that the side edges join to form the strip into a cylindrical shape. The guide shoes also compress the material prior to its advancement into the curing apparatus. Continuous molding processes of the prior art generally use axially symmetric folding shoes, such as conical or parabolic shoes, to form and compress the strips into cylindrical shape.
One of the problems associated with the continuous insulation manufacturing processes of the prior art is that the portion of the product near the seam created where the sides of the strip material are adjoined, usually at the top of the cylindrical insulation piece, is structurally weak. Advantageously, the edges of the strip material will be bonded together so that the seam is neither visually nor structurally evident. In practice, however, the seams of pipe insulation made by the devices of the prior art are weak, and subsequent fabrication operations, such as slitting pipe insulation pieces for packaging, often result in defective products due to separation at the seam. Another problem associated with the continuous molding of pipe insulation material is that the forces placed on the strip material passing through the folding shoe are sometimes so great that breakage or unacceptable folding of the strip material occurs. The use of axially symmetric folding shoes contributes to undue tension in the strip material. The apparatus and method of this invention are directed towards solution of the above problems.